a) Field of the Invention
This invention relates to a seatbelt system provided with a retractor.
b) Description of the Related Art
As a retractor in a seatbelt system for safely holding an occupant of a vehicle or the like in a seat, an emergency locking retractor has been used conventionally. This emergency locking retractor is equipped with an emergency locking mechanism for physically locking the retractor by an inertia sensing member in response to a sudden acceleration, collision or deceleration, thereby effectively and safely restraining the occupant.
Such emergency locking retractors includexe2x80x94like seatbelt retractors disclosed, for example, in U.S. Pat. Nos. 3,929,300, 4,366,934 and JU 2-45088 Bxe2x80x94those equipped with a locking member that a locking member arranged on an end of a retracting spindle, on which a webbing is wound, is brought into meshing engagement with a locked portion of a retractor base in the event of a vehicular emergency to prevent any further rotation of retracting spindle in a webbing-withdrawing direction.
In the above-described locking member, teeth formed on an edge of a retracting spindle through-hole in the retractor base, through which the retracting spindle extends, or teeth formed on a latch plate arranged in association with the retracting spindle through-hole are used as a locked portion, while a locking plate or pawl rotatable together with the retracting spindle is used as a locking member. In the event of a vehicular emergency, these locking member and locked member mesh with each other to prevent any further rotation of the retracting spindle in the webbing-withdrawing direction.
When an impact force resulting from a collision is extremely large, on the other hand, the tension on the webbing progressively increases as time goes on subsequent to the collision. This causes a sudden deceleration on the occupant""s body, so that the load applied to the occupant from the webbing becomes extremely large. With a view to coping with this problem, various seatbelt retractors have also been proposed. These seatbelt retractors are each equipped with an energy-absorbing mechanism that, when the load acting on the webbing becomes equal or greater than a preset value, the webbing is withdrawn over a predetermined length to absorb a substantial portion of an impact which would otherwise occur on the occupant""s body, so that the occupant""s body can be protected more positively. As a seatbelt retractor of such a construction, the xe2x80x9cenergy absorbing mechanism especially for use in a safety belt systemxe2x80x9d disclosed in U.S. Pat. No. 3,741,494 is known.
The above-described energy absorbing mechanism is provided with a retracting member (bobbin) as an element through which a force is transmitted and also with a holder (retractor base) rotatably arranged relative to the retracting member. A torsion bar is also arranged as an energy absorbing member between the retracting member and the holder. In the event of a vehicular emergency, a gear (locking member) arranged on an end portion of the torsion bar is locked by a locking lever, whereby the torsion bar is connected with the holder such that the torsion bar cannot rotate in a webbing-withdrawing direction. On the other hand, an opposite end of the torsion bar has been unrotatably connected with the retracting member in advance. When a torque acts on the retracting member in the webbing-withdrawing direction, the torsion bar itself is twisted about an axis thereof and hence undergoes a plastic deformation. As a consequence, a substantial portion of impact energy which would otherwise act on the occupant""s body is absorbed as deforming work for the torsion bar as the energy absorbing member.
In this case, however, no limitation is imposed on the extent of torsion of the torsion bar (energy absorbing stroke). It may, however, be desired to limit the extent of torsion in some instances. As an example of a seatbelt retractor having an energy absorbing mechanism which is equipped with a stop member for limiting an energy absorbing stroke, there is the xe2x80x9cretractor for safety belt systemxe2x80x9d proposed in JP 57-6948 (hereinafter referred to as xe2x80x9cConventional Art 1xe2x80x9d).
According to the energy absorbing mechanism in the above-described retractor, a latch plate (locking member) mounted on a webbing-retracting spindle is fixedly provided with a first member such that the first member is coaxial with the webbing-retracting spindle. Further, the webbing-retracting spindle is fixedly provided with a second member such that the second member is located opposite the first member. Over a groove formed on at least one of the first member and the second member, a roller is arranged as an energy absorbing member such that the roller is interposed between the first member and the second member. When the roller rolls over the groove, it undergoes a plastic deformation. As a consequence, a substantial portion of impact energy which would otherwise act on the occupant""s body is absorbed as deforming work for the groove. In addition, a key is planted as a stopping member at a point close to a final end of the groove to prevent any further advancement of the roller, thereby imposing a limitation on an energy absorbing stroke.
Further, an emergency locking retractor for a seatbelt system, said retractor being equipped with an energy absorbing mechanism, is disclosed, for example, in U.S. Pat. No. 5,772,144.
U.S. Pat. No. 5,772,144 (hereinafter referred to as xe2x80x9cConventional Art 2xe2x80x9d) also discloses, as conventional art, a construction in which a pawl (stopping member) mounted on a side wall of a reel shaft (bobbin), on which a webbing is wound, is brought into engagement with one of teeth (internal teeth) formed on a circumferential edge of a reel-shaft supporting opening in a base frame (retractor base) (an opening formed in a side plate of the retractor base) to prevent any further rotation of the bobbin in a webbing-withdrawing direction.
In the case of the stopping member making use of the key as disclosed in Conventional Art 1, a large load acts on the key upon actuation of the second pawl. The key is therefore required to retain strength sufficient to withstand a load from the second pawl. Further, at the end of the absorption of energy, the rotation of the webbing-retracting spindle is prevented by a latch plate locked by a retractor base. Accordingly, the roller, the first and second members and the like, all of which are arranged between the latch plate and the webbing-retracting spindle, are also required to have strength sufficient to withstand a load applied until the rotation of the webbing-retracting spindle is finally prevented. To ensure restraint of an occupant in the event of a vehicular emergency, the parts arranged between the latch plate and the webbing-retracting spindle are all required to have sufficient strength. This however requires use of costly materials and/or complex machining, leading to a problem that higher manufacturing cost is unavoidable.
In the case of the seatbelt retractor disclosed as its conventional art in Convectional Art 2, on the other hand, adoption of such a design that the stopping member is brought into contact with a wall portion formed on the side wall of the bobbin upon engagement of the stopping member with the internal teeth formed in the side wall of the retractor base in the event of a vehicular emergency such as a vehicular collision results in application of a considerable load to the wall portion of the bobbin because a preventing force produced upon prevention of rotation of the bobbin acts on the bobbin via the stopping member. When a load applied from the stopping member acts directly on a particular portion of the bobbin as described above, the bobbin itself must have sufficient strength. To provide the bobbin with such sufficient strength, it is necessary to reinforce the bobbin at the particular portion to which loads are applied, to use a costly material for the bobbin itself and/or to use one or more complex machining methods. This has led to a problem that higher manufacturing cost is unavoidable.
With the foregoing circumstances in view, the present invention has as an object thereof the provision of a seatbelt system provided with a retractor which is economical despite its possession of sufficient strength.
The above-described object of the present invention can be achieved by A seatbelt system provided with a retractor, wherein the retractor comprises:
a retractor base having a pair of side plates;
a shaft rotatably mounted on the retractor base;
a bobbin fixed on an end of the shaft and carrying a webbing withdrawably wound thereon;
a locking member fixed on an opposite end of the shaft;
an emergency locking mechanism for connecting the locking member and one of the side plates of the retractor base in an event of a vehicular emergency such that the locking member is prevented from rotation in a webbing-withdrawing direction; and
a bobbin locking mechanism arranged between the retractor base and the bobbin such that, when rotation of the locking member is prevented by the emergency locking mechanism, torsion of the shaft is limited to a predetermined extent and the bobbin is connected to the other side plate of the retractor base.
According to the above-described construction of the present invention, the bobbin is prevented from rotation in the webbing-withdrawing direction in the event of a vehicular emergency by the engagement of the locking member with the one side plate of the retractor base. Further, when a rotational torque of a predetermined value or greater is applied between the bobbin and the locking member by a load acting on the webbing, a substantial portion of impact energy is absorbed owing to a deformation of an energy absorbing member (shaft). When relative rotation between the bobbin and the locking member reaches a predetermined extent, the bobbin locking mechanism is actuated such that the rotation of the bobbin is prevented by the other side plate of the retractor base. This makes it possible to adequately control the extent to which the energy absorbing member undergoes a deformation for the absorption of energy.
Upon completion of the absorption of the energy, any further rotation of the bobbin is prevented directly by the retractor base via the bobbin locking mechanism. It is therefore sufficient for parts such as the locking member if they can withstand only a force applied to deform the energy absorbing member arranged between the bobbin and the locking member. Concerning the retractor base, it is possible to reduce its reinforcement by separately assigning the function to engage the locking member and the function to engage the bobbin via the bobbin locking mechanism to the respective side plates. This has made it possible to provide a seatbelt system equipped with a retractor which is economical despite its possession of sufficient strength.
The above-described object of the present invention can also be achieved by a seatbelt system provided with a retractor, wherein the retractor comprises:
a retractor base,
a shaft rotatably mounted on the retractor base,
a bobbin fixed on an end of the shaft and carrying a webbing withdrawably wound thereon,
a locking member fixed on an opposite end of the shaft,
an emergency locking mechanism for connecting the locking member and the retractor base in an event of a vehicular emergency such that the locking member is prevented from rotation in a webbing-withdrawing direction, and
a bobbin locking mechanism arranged between the retractor base and the bobbin such that, when rotation of the locking member is prevented by the emergency locking mechanism, torsion of the shaft is limited to a predetermined extent and the bobbin is connected to the retractor base;
wherein the bobbin locking mechanism has an engaging member and a control member, the engaging member is supported on the bobbin and is movable between a first position, where the engaging member is out of engagement with the retractor base, and a second position, where the engaging member is in engagement with the retractor base, and the control member has flexibility, connects the locking member and the engaging member with each other, and, when torsion of the shaft has reached a predetermined extent, brings the engaging member from the first position to the second position.
According to the above-described construction of the present invention, the bobbin is prevented from rotation in the webbing-withdrawing direction in the event of a vehicular emergency by the engagement of the locking member with the retractor base. Further, when a rotational torque of a predetermined value or greater is applied between the bobbin and the locking member by a load acting on the webbing, a substantial portion of impact energy is absorbed owing to a deformation of an energy absorbing member (shaft). When relative rotation between the bobbin and the locking member reaches a predetermined extent, the rotation of the bobbin is prevented by the bobbin locking mechanism provided with the flexible control member. This makes it possible to adequately control the extent to which the shaft undergoes a deformation for the absorption of energy.
Upon completion of the absorption of the energy, any further rotation of the bobbin is prevented directly by the retractor base via the bobbin locking mechanism. It is therefore sufficient for parts such as the locking member if they can withstand only a force applied to deform the energy absorbing member arranged between the bobbin and the locking member.
It is therefore possible to provide a seatbelt system equipped with a retractor which is economical despite its possession of sufficient strength.
The above-described object of the present invention can also be achieved by a seatbelt system provided with a retractor, wherein the retractor comprises:
a retractor base with an engaged portion formed thereon;
a bobbin rotatably supported on the base and having fitted recesses;
a sleeve having fitting faces, which are maintained in engagement with the fitted recesses, and a shaft portion forming a spindle for the bobbin; and
a pawl supported in contact with the sleeve and engageable with the engaged portion of the base.
According to the above-described construction of the present invention, the pawl is supported in contact with the sleeve when the pawl is actuated in the event of a vehicular emergency and the bobbin is prevented from any further rotation in a webbing-withdrawing direction relative to the retractor base.
An impactive load received from the pawl is therefore applied to the bobbin via the sleeve in such a way that it is spread to fitted portions between the sleeve and the bobbin. As a consequence, it has become no longer necessary to reinforce the bobbin, for example, to use a costly material for the bobbin, thereby making it possible to provide a seatbelt system equipped with a retractor which is economical despite its possession of sufficient strength.
The shaft portion for the bobbin can be formed integrally with the sleeve.